It is narrated from Yazid bin Asam (may Allah have mercy on him) (he is the nephew of Maymunah, may Allah be pleased with her) that the Messenger of Allah ﷺ married Maymunah while he was in a state of being lawful (not in Ihram).
Hadith Referenceمسند الإمام الشافعي / كتاب الحج / 876
Hadith Takhrijاسناده مرسل والحديث صحيح أخرجه البيهقي : 210/7 - وفى المعرفة السنن والآثار له (2886) ۔ وانظر (874)